Electron tube



May 3, 1949. w. w. EITEL ETAL ELECTRON TUBE Filed Oct. 29, 1945 7 w 5 m 5 6 w 4 A a Q x n. ////////%/%////////A// 6 m z/ z 4 o m 2 W A,- u u u III IMHHI I H I 5 M W J 4 w y y 5 w 7 J m INVENTORS WILL/AM (M E/TEL dacx AME Caz. ousH ATTORNEY Patented May 3, 1949 ELECTRON TUBE William W. Eitel,

Woodside, and lick A. Mc-

Cullough, Millbrae, Calif.,=assignors to Eitei- McCullough, lnc., S ration of California amilrnno, Calif com-- Application October 29, 1945, Serial No. 625,200.

2 Claims.

Our invention relates to electron tubes, and more particularly to multi-grid tubes, such as tetrodes.

It is among the objects of our invention to provide improvements in the mounting and terminal arrangement for the several electrodes in an electron tube, whereby the tube is better adapted for higher frequency operation.

Another object is to provide improvements of the character described in a tube of the external anode type.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth-in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of the claims.

Referring to the drawing:

The figure of the drawing is a vertical sectional view of a tube embodying the improvements of our invention.

In terms of broad inclusion, our tube comprises a plurality of electrodes and'a terminal arrangement therefore, including a grid terminal located on the tube coaxial with and opposite to an anode. In our preferred construction, a pair of coaxial grid terminals are provided, one for a control grid and the other for a screen grid, the screen grid terminal being preferably formed by a metallic header at one end of the tube envelope. The preferred tube includes an external anode having a portion extending into. the envelope opposite the header, and also preferably includes a shield interposed between the anode and the control grid terminal.

In greater detail, and referring to the drawing, our preferred tube structure comprises an envelope embodying an external anode 2 so arranged that a portion of the anode extends within the envelope. The anode preferably comprises a tubular metallic body 3 supported on the envelope by a reversely extending fiange l brazed at one end to anode body 3 and sealed at the other end to vitreous envelope section 6. Anode flange 4 extends upwardly and is spaced from the anode body to provide a reentrant anode structure with a recess formed between the flange and body I, the flange being preferably curved to provide a downturned sealing rim.

Anode body I may be of any suitable metal, such as copper or nickel, and fiange 4 is of a metal having an expansion characteristic matching that of the glass in envelope section 6. A metallic tuin terminal ll.

bulation l secured to the upper end of the cupshaped anode body provides an exhaust duct.' After evacuation, the tubulation is pinched of! at tip l.

A plurality of electrodes including a cathode I,

ode may be employed if desired. Grids H and I! are preferably of the cage type supported from the bottom and having upper free ends. This free ended electrode structure is important from the standpoint of tube assembly.

A metallic header I3 is provided at the lower end of the tube, opposite the anode, and comprises a dish-shaped piece having a bottom wall l4 and an upturned flange I 6 sealed to wall section 6, the header being of a metal having an expansion characteristic matching that of the glass. A central control grid terminal I1 and a pair of -cathode terminals II and I! are supported on and insulated from the header.. These terminals may be of any suitable construction, those illustrated comprising tubular members extending through apertures in bottom wall II and supported by vitreous rings 2| sealed between the tubular members and the header wall.

Cathode O is supported on and electrically connected to terminals l8 and IS. A center rod 22 connected to the ,upper end of the filament has a lateral portion 23 fastened to a stud 24 secured The lower end of the filament is connected to a sleeve 28' carried by a bracket 21 on an arm 28 fastened to stud 29 secured in terminal ll.

Control grid II has its lower end connected to a sleeve 3! carried by bracket 32 on arms 32 fastened to a stud 34 secured in terminal ll. It will be observed that control grid terminal I! is arranged on the envelope opposite to and in coaxial alignment with the anode, which arrangement is particularly desirable in a tetrode for higher frequency operation.

Screen grid I2 is supported on and electrically connected to header is, the supporting meansfor this grid preferably including an electrostatic shield interposed betweenthe anode and the control grid conductor means. The preferred structure comprises adisk-like shield 36 having a central aperture ll aligned with the screen grid and secured to a mounting ring 31 fastened to the.

55 inner surface of the annular header flange II.

As shown, the lower portions of the screen grid wires are spread somewhat to increase the spacing from sleeve 3|, and have outturned ends secured between disk 36 and a washer 38. A slight offset 39 in disk 36 enhances its mechanical rigidity.

By this arrangement the screen grid and connected shield form electrostatic shielding means isolating the anode from the control grid structure. While we prefer to mount the screen grid directly on shield 36, for purposes of simplicity of structure, it is apparent that the screen grid could be extended through aperture 35 and supported separately from the shield. In the latter 1 case the screen grid and shield could be connected, either internally or externally of the envelope.

In the preferred structure illustrated, the header flange I6 provides a terminal ring for the screen grid, which terminal ring comprises part of the envelope side wall and lies coaxial with the anode, so that the control grid terminal and screen grid terminal and anode are all disposed about a common axis suitable for concentric line circuits. Our tube is adapted for plugging into a socket structure, and-in order to .limit downward movement of the tube in a socket, we preferably form an ofiset 4| in flange l6 to provide a stop for the socket fingers.

A suitable cooler 42 is secured to the anode for removal of heat. In an air cooled tube, as shown, the cooler comprises a core 43 carrying radial fins 44. Core 43 is of a metal having good heat conducting properties, such as copper, and preferably extends into the recess of the reentrant anode so that removal of heatalong the entire outer surface of anode is assured.

An external type of anode is preferred in our tube, because of the greater heat dissipating capabilities of such an anode. While a full external anode may b employed, we prefer to use a type of external anode having portions extending into the envelope. The latter type shortens the overall length of the tube and improves it electrically for higher frequency operation. As illustrated, the anode flange 4 provides a sealing rim which lies above the lower end of the anode, thereby providing ample glass length in section 6 between the anode and grid terminal ring it for insulation purposes, while at the same time providing a compact electrode structure with short, low inductance leads to the electrodes. It is understood, however, that certain features of our invention such as the electrode terminal arrangement, may be used to advantage in tubes of the radiation cooled type (wherein the anode lies wholly within the envelope) as well as in tubes of the external anode type.

We claim:

1. An electron tube comprising an envelope having an external anode at one end and a control grid terminal coaxial with the anode at the opposite end, an annular screen grid terminal coaxial with the control grid terminal and interposed in the envelope wall between the anode and said control grid terminal, a cathode in the envelope projecting into the anode, a control grid in the envelope surrounding the cathode and connected to the control grid terminal, a screen grid in the envelope surrounding the control grid and connected to the screen grid terminal, and a shield connecting the screen grid and screen grid terminal, said terminal and shield serving to screen the control grid terminal from the anode.

2. An electron tube comprising an envelope having an external anode at one end, a cathode and control grid and screen grid in the envelope, a control grid terminal on the envelope, an annular screen grid terminal on the envelope interposed between the control grid terminal and anode, said screen grid terminal being coaxial with the control grid terminal, and a shield carrying .the screen grid, supported on the screen grid terminal and located between the anode and said control grid terminal, said shield and terminal serving to screen the control grid terminal from the anode.

I WILLIAM W. EITEL.

JACK A. MCCULLOUGH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,583,463 Houskeeper May 4, 1926 1,708,939 Crawford Apr. 16, 1929 1,927,629 Edelman Sept. 19, 1933 2,011,008 Oosterhuis Aug. 13, 1935 2,112,958 Glutton et al Apr. 5, 1938 2,238,596 Mouromtseif et a1. Apr. 15, 1941 2,246,125 Crawford June 17, 1941 2,289,984 Mouromtsefl et a1. July 14, 1942 2,310,147 Dailey Feb. 2, 1943 2,310,936 Chevigny Feb. 16, 1943 2,317,442 Chevigny Apr. 27, 1943 2,345,794 Chevigny Apr. 4, 1944 2,402,602 Chevigny June 25, 1946 

